If you are new to Unix, you probably should go out and buy some books and do some reading. The Unix FAQ contains a number of references to books and Usenet news groups which should help you out. You can also take a look at the User-Friendly Unix FAQ.
Linux is an implementation of Unix. The Linux Documentation Project (LDP) collects a number of HOWTOs and online books relating to Linux. Most of these documents can be installed locally; just install the doc-linux-html package (HTML versions) or the doc-linux-text package (ASCII versions), then look in /usr/share/doc/HOWTO. International versions of the LDP HOWTOs are also available as Ubuntu packages.